BACILLUS-SUBTILIS GTAB ENCODES UDP-GLUCOSE PYROPHOSPHORYLASE AND IS CONTROLLED BY STATIONARY-PHASE TRANSCRIPTION FACTOR-SIGMA-B

Transcription factor sigma(B) of Bacillus subtilis controls a large st ationary-phase regulon, but in no case has the physiological function of any gene in this regulon been identified. Here we show that transcr iption of gtaB is partly dependent on sigma(B) in vivo and that gtaB e ncodes UDP-glucose pyrophosphorylase. The gtaB reading frame was initi ally identified by a sigma(B)-dependent Tn917lacZ fusion, csb42. We cl oned the region surrounding the csb42 insertion, identified the readin g frame containing the transposon, and found that this frame encoded a predicted 292-residue product that shared 45% identical residues with the UDP-glucose pyrophosphorylase of Acetobacter xylinum. The identif ied reading frame appeared to lie in a monocistronic transcriptional u nit. Primer extension and promoter activity experiments identified tan dem promoters, one sigma(B) dependent and the other sigma(B) independe nt, immediately upstream from the proposed coding region. A sequence r esembling a factor-independent terminator closely followed the coding region. By polymerase chain reaction amplification of a B. subtilis ge nomic library carried in yeast artificial chromosomes, we located the UDP-glucose pyrophosphorylase coding region near gtaB, mutations in wh ich confer phage resistance due to decreased glycosylation of cell wal l teichoic acids. Restriction mapping showed that the coding region ov erlapped the known location of gtaB. Sequence analysis of a strain car rying the gtaB290 allele found an alteration that would change the pro posed initiation codon from AUG to AUA, and an insertion-deletion muta tion in this frame conferred phage resistance indistinguishable from t hat elicited by the gtaB290 mutation. We conclude that gtaB encodes UD P-glucose pyrophosphorylase and is partly controlled by sigma(B). Beca use this enzyme is important for thermotolerance and osmotolerance in stationary-phase Escherichia coli cells, our results suggest that some genes controlled by sigma(B) may play a role in stationary-phase surv ival of B. subtilis.